RegEx - Using Templates

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Have an issue with Substitutions. I have a config file that holds all my regular expressions. Problem is the subsitutions don't work. Example:

  $text = 'Cheese.Bacon';
  $v1 = '(\w+)\.(\w+)';
  $v2 = '$2\.$1';
  $test =~ s/$v1/$v2/;
[download]

The end result should be:

  $text = 'Bacon.Cheese';
[download]

This is what I get:

  $text = '$2\.$1';
[download]

How do I get the Substitutions to work correctly.

Thanks in advance.

Edit by tye, title, remove BR tags, add CODE tags

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Re: RegEx - Using Templetes by Zaxo (Archbishop) on May 29, 2003 at 02:48 UTC
You have several problems there. Your substitution string must be evaluated twice to get the $1 and $2 interpolated. Evaluation, however, does not like the regex style backwhack in $v2, and will simply take a bare dot to mean concatenation. Modify your code to something like this: `$text = 'Cheese.Bacon'; $v1 = qr/(\w+)\.(\w+)/; $v2 = 'qq($2.$1)'; $text =~ s/$v1/$v2/ee;` [download] I added use of qr() for $v1, but what you had was ok. After Compline, Zaxo	[reply] [d/l]
Re: Re: RegEx - Using Templetes by Anonymous Monk on May 29, 2003 at 13:19 UTC
You guys are awesome. the qq{...} worked perfectly. Thanks so much!	[reply]
Re: RegEx - Using Templetes by Enlil (Parson) on May 29, 2003 at 02:54 UTC
Though your question has been answered there is some good discussion in $1 in variable regex replacement string about this sort of thing. -enlil	[reply]
Re: RegEx - Using Templates by VSarkiss (Monsignor) on May 29, 2003 at 02:44 UTC
~~The easiest thing is to use the `/e` modifier: `$text =~ s/$v1/$v2/e;`~~Read more about it in perlre. Update This is wrong; follow Zaxo's advice below.	[reply] [d/l] [select]